# [ICEM] 3d blocking - divergence in Fluent

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February 22, 2013, 15:51
3d blocking - divergence in Fluent
#1
New Member

jyh
Join Date: Nov 2012
Posts: 25
Rep Power: 5
Hi guys, I'm stuyding a fairing for Human Powered Aircraft.

I managde to make hexa grid using ICEM-CFD. (see picture)

I use O-grid around fairing, and set 1st cell distance to 0.04 for y+<=1.
I checked 2x2x2 determinant (above 0.7) , and angles(above 18 deg).

and I convert to unstructured mesh, and set BC.

After I ran the simulation in Fluent, the residuals of continuity diverged at 200~300 iterations. (check, scaling also done)

The flow condition is
U=8m/s
k-omega SST (even laminar model failed, too)
others : default for quick trying.

I'd like you to see ICEM files for detail, I linked it below.
https://www.dropbox.com/s/h3drel9swnyfb1l/diver.zip

(You should uncheck 'SOLID' part whick is inner block in fairing.)

I hope someone helps me for finding my fault.

best&regards.
Attached Images
 1.jpg (98.0 KB, 24 views) 2.jpg (94.8 KB, 25 views) 3.jpg (95.7 KB, 23 views)

Last edited by jyh3134; February 22, 2013 at 20:31.

 February 22, 2013, 20:18 solve #2 New Member   jyh Join Date: Nov 2012 Posts: 25 Rep Power: 5 I solved the problem by regenerating new mesh by myself. The aspect ratio caused this problem i think. Thanks for your interest. Best & Regards

 February 23, 2013, 06:13 #3 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,299 Blog Entries: 6 Rep Power: 43 Look on this blocking. Fairing3 has o-grid in the wake region. https://dl.dropbox.com/u/68746918/Fairing2_Far.zip https://dl.dropbox.com/u/68746918/Fairing3_Far.zip

 February 23, 2013, 08:20 Thanks Far!! #4 New Member   jyh Join Date: Nov 2012 Posts: 25 Rep Power: 5 Above all, I'm very glad to receiving your help. I like your first suggestion due to easy being easy to understand blocking. You should split around SOLID part and wake region with o-grid after split tail of fairing with o-grid(for inner circle), right? and some other blocking strategy of yours are very helpful for me. It's well worth enough to run simulation again with new mesh on your suggestion, and I'll let you know the results in Fluent. ----------------------------------------------------------------- The simulation failed again. So I'm certain that working in geometry had some error.(dividing parts or rapiaring geometry topology,etc.) So I need to make new blocking again like yours with another geomety which was worked well. It's very similar to previous one, but not identical, so can't match blk file. Anyway, Thanks for your help again, and I have a question to you personally. Are you working in ANSYS inc? I know SIMON is, and think that you should be. I believe that the greatful help and support of yours(likes threads, YOUTUBE videos, etc.) is one of the strengths of ANSYS. Best& regards

February 23, 2013, 09:35
#5
Super Moderator

Sijal
Join Date: Mar 2009
Posts: 4,299
Blog Entries: 6
Rep Power: 43
Quote:
 You should split around SOLID part and wake region with o-grid after split tail of fairing with o-grid(for inner circle), right?
After making o-grid around surface (fairing), I made split at some lengths downstream. Then I chose those downstream blocks (use index control) and made the o-grid. Blocking may look like something complex due to many edges.

Quote:
 So I'm certain that working in geometry had some error.(dividing parts or rapiaring geometry topology,etc.) So I need to make new blocking again like yours with another geomety which was worked well. It's very similar to previous one, but not identical, so can't match blk file.
No need to re-create blocking. If your geometry is similar, you can use older blocking with minor adjustments.
Exporting blocking/mesh for a similar geometry

Quote:
 Are you working in ANSYS inc? I know SIMON is, and think that you should be. I believe that the greatful help and support of yours(likes threads, YOUTUBE videos, etc.) is one of the strengths of ANSYS.
I hope, one day I will be there...

PS : what are the units and boundary conditions you are using... Is there any thread in Fluent section?

 February 23, 2013, 11:59 #6 New Member   jyh Join Date: Nov 2012 Posts: 25 Rep Power: 5 I used BC with Velocity Inlet(upstream, top,bottom,side) , Pressuare Outlet and symmetry. Because the flow is incompressible. ( U=8m/s) Re is about 1.5e6, so I used k-omega SST turbulent model. Thanks for kind explain, the index control still isn't familiar with me. I'll try it again tommorow.(now I'm busy to write onther report.) and also wish you get a reward for being so helpful. You'll be there I'm sure. BTW is there more learing material or examples about 3d blocking? I read tutorial manual and watched videos(ANSYS inc, yours(turboengineer, right?)), lots of threads in this forum and managed to try them. But still I can't make structured mesh with the geometry(my final goal) of my study. someone probably can tell me that the theoretical training already has done, that's problem about my experience and efforts. But I want to know how you can improve your blocking skills. and i think many people want to know, too. Best& Regards

February 23, 2013, 12:24
#7
Super Moderator

Sijal
Join Date: Mar 2009
Posts: 4,299
Blog Entries: 6
Rep Power: 43
Did you check the mesh quality in Fluent?

You made the model in mm or m?

Quote:
 But I want to know how you can improve your blocking skills. and i think many people want to know, too.
You keep (and other) on giving me geometries

 February 23, 2013, 12:42 #8 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,299 Blog Entries: 6 Rep Power: 43 I have planned to work on following cases (from geometry to post processing): 1. Wing body (different configurations) 2. Automotive (Ahmed body) 3. Centrifugal and axial compressor 4. Centrifugal pump and volute 5. Wing 6. Heat transfer (preferably heat exchanger and film cooling in gas turbine) 7. Vertical and horizontal axis wind turbine 8. Formula one 9. Any thing else in demand We plan to provide high quality solution from scratch to final report. I am also planning to add T-grid, ICEM tetra surface meshing (Patch dependent and patch independent). I also want to attempt full hexa meshing on Helicopter and complex air-craft. We will put ready-made solution and also on call one-to-one sessions. cfd seeker likes this.

February 23, 2013, 13:07
#9
Senior Member

Join Date: Mar 2011
Location: Germany
Posts: 422
Rep Power: 12
Quote:
 Originally Posted by Far I have planned to work on following cases (from geometry to post processing): 1. Wing body (different configurations) 2. Automotive (Ahmed body) 3. Centrifugal and axial compressor 4. Centrifugal pump and volute 5. Wing 6. Heat transfer (preferably heat exchanger and film cooling in gas turbine) 7. Vertical and horizontal axis wind turbine 8. Formula one 9. Any thing else in demand We plan to provide high quality solution from scratch to final report. I am also planning to add T-grid, ICEM tetra surface meshing (Patch dependent and patch independent). I also want to attempt full hexa meshing on Helicopter and complex air-craft. We will put ready-made solution and also on call one-to-one sessions.
Nice idea . What is the name of your company/project so that we can advertise you

 February 23, 2013, 13:23 #10 New Member   jyh Join Date: Nov 2012 Posts: 25 Rep Power: 5 https://www.dropbox.com/s/fza18hdf6n...0for%20HPA.zip my recent prj, tin file is here and unit is mm. It made no problem. quality of old one in Fluent I checked, Minimum Orthogonal Quality : 2.29615e-05 !! Maxiimum Aspect Ratio : 1.24145e+06 This value is not equal to the value I check quality of converted uns mesh in ICEM-CFD (above 0.3) How it can be??? By the way.. Oh, most of projects you listed are present in your Youtube channel. I'll try more and more your projects even something seems to be not to associated with my study. Everything is helpful I think.

 February 23, 2013, 13:31 #11 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,299 Blog Entries: 6 Rep Power: 43 These tutorials are available, but I want to increase their quality 10 times with written material and voice. Mesh is too fine. It should not exceed 0.5-0.6 million.

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